Comparison between extinctions estimated from UV absorption lines in the spectra of nearby white dwarfs and extinction values integrated in a preliminary 3D map (see text). Left: Using Pii ion columns from Lehner et al. (2003) and phosphorus depletions from Jenkins (2009). Black arrows correspond to estimated negative values and show the corresponding upper limits. The dot-dashed black line is a linear fit using only positive values. Right: Using N(H) columns estimated by Jenkins (2009) from P, O, Si, and Fe ions. The dot-dashed black line is reported from the left panel. Both estimates indicate a positive bias on AV of about 0.01 mag.